Gusset Joints Research Articles

Analytical assessment of low‐ and high‐cycle fatigue behavior of welded components considering the linear hardening model

AbstractWelded components are highly vulnerable to fatigue failures due to stress concentrations and material imperfections. This study develops an analytical framework that predicts both high‐cycle (HCF) and low‐cycle (LCF) fatigue lives of welded joints using a structural strain parameter. By employing a linear hardening model, the method effectively translates structural stress into structural strain, providing a reliable metric for assessing fatigue life, especially in LCF conditions. Validated against experimental data from 62 longitudinal gusset joints, the approach proves both reliable and practical. This simplified method facilitates easier fatigue assessments, encouraging its wider use and potential standardization in engineering, thus improving the predictability of welded structures' performance.

Experimental and numerical analysis on the post-fire flexural behavior of aluminum alloy gusset joints

Regarding the damage incurred by aluminum alloy latticed shells under fire loads, a crucial aspect in assessing structural integrity is examining the residual bearing capacity of aluminum alloy gusset (AAG) joints. Consequently, this paper conducted experimental and numerical analyses on the post-fire flexural behavior of AAG joints. Initially, twelve AAG joints underwent post-fire tests, revealing that the failure patterns differed between thin-plate joints (exhibiting block tearing of gusset plates) and thick-plate joints (exhibiting member buckling). Notably, the initial stiffness approximately remained constant, while a trilinear relationship emerged between the ultimate flexural bearing capacity and the maximum post-fire temperature. Subsequently, finite element (FE) analysis was carried out, and the accuracy of FE models was verified by comparing the FE results with the test results. A comprehensive parametric analysis, considering various plate thicknesses, post-fire temperatures, and aluminum alloy brands, was then conducted. Ultimately, employing statistical regression, theoretical equations were formulated to estimate both bending stiffness and bearing capacity for AAG joints after exposure to fire.

Crashworthiness of AAG joints with a foam aluminum layer gusset plate

The gusset joint is the most widely used joint system in an aluminum alloy single-layer reticulated shell structure; it plays a vital role in the spatial grid structure. In this paper, the effects of different thicknesses of aluminum alloy gusset plates on the dynamic response and failure modes of aluminum alloy gusset (AAG) joints were studied by impact tests of three specimens. The test results show that the failure modes of AAG joints are a slight depression of the gusset plate, the local buckling of members, the local distortional buckling of members, and tearing of the lower flange and a web of members. The AAG joint inclines along the direction of the failed member and collapses. The finite element model of the AAG joint was established using ANSYS software. The stress, displacement, and deformation modes in the test and numerical simulation results were compared and analyzed, and the rationality of the numerical simulation results was verified. Based on the failure mode of the specimens, a design method for improving the impact resistance of AAG joints with aluminum foam layer gusset plate (AFLGP) is proposed. The numerical simulation results show that an AAG joint with an AFLGP effectively reduces the maximum peak value of impact loads through the deformation of the aluminum foam. In the elastic and elastic-plastic stages, AAG joint with AFLGP had better impact resistance, and the energy absorbed by its rods was 25.44% ∼ 30.36% lower than that of AAG joints alone. Finally, the influence of the thickness of the AFLGP on the impact force and energy absorption of the AAG joint was studied. The aluminum foam gusset layer plate is approximately twice as thick as the aluminum alloy gusset plate had the best protection effect on the AAG joint.

Experiment investigation and theoretical analysis of an improved aluminum alloy gusset joint

This study presents enhancements made to traditional aluminum alloy gusset (AAG) joints, including the integration of a central stiffening (CS) system, an inter-panel stiffening (IS) system, and a peripheral stiffening (PS) system. Three sets of tests on a full-scale specimen are conducted to investigate the improved AAG joint's axial stiffness, in-plane and out-of-plane bending stiffness, as well as ultimate load-bearing capacity. Nonlinear refined finite element models (FEMs) are established and validated through experimental results. Theoretical mechanical models are developed by integrating experiments and FEMs. These models elucidate the contribution of the stiffening systems to the joint's mechanical performance. The CS system is proven to significantly assist in load transfer, particularly in out-of-plane bending conditions. The IS system enhances overall inter-panel integrity, especially during the plastic deformation phase under out-of-plane bending moments. The PS system improves joint stiffness by participating in load transmission under both axial load and in-plane bending moments. Compared to traditional AAG joints, the combined effects of the three stiffening systems enhance overall structural integrity, stiffness, and load-bearing capacity. This enables the full utilization of component material properties and provides excellent ductility before failure occurs.

Experimental investigation of aluminium alloy gusset joints’ dynamic response to lateral impact loads: Evaluating the influence of gusset plate bending stiffness

The traditional aluminium alloy gusset plate (AAG) joint is commonly regarded as a representative semi-rigid joint characterized by limited stiffness. This deficiency in stiffness significantly hampers its capacity for load transmission and resistance against progressive collapse in spatial grid structures. Notably, the dynamic response characteristics of semi-rigid joints, especially when subjected to short-term, highly intense loads such as impacts and explosions, deviate substantially from those of rigid joints. This research examines the dynamic failure behavior of six distinct traditional AAG joints with varying degrees of stiffness when subjected to impact loads. The first group comprises three specimens where the variance in AAG joint stiffness is achieved by altering the gusset plate’s diameter. The second group comprises three specimens aiming to manipulate the AAG joint’s stiffness by modifying the gusset plate’s thickness. The study yielded comprehensive data, including stress profiles, displacement patterns, acceleration time history curves, and failure modes of AAG joints. The experimental findings revealed that both groups of AAG joints under lateral impact loads exhibited brittle failure. The predominant failure modes included the rupture of the H-shaped aluminium alloy beam, distortional buckling of the beam, and warping of the thinner gusset plate. It is evident from the stress, displacement, and acceleration time history curves that the AAG joint adheres to the characteristics of a typical semi-rigid joint, and the diameter and thickness of the gusset plate exert significant influence on the AAG joint’s dynamic response. Subsequently, the six test conditions were simulated using ANSYS/LS-DYNA software. This simulation considered the stress distribution, impact force time history curves, and strain energy time history curves of AAG joints. It facilitated a detailed discussion of the failure mechanism underlying AAG joints when subjected to lateral impact loads.

Study on the static stability of aluminum alloy single-layer spherical reticulated shell

In order to study the static stability of an aluminum alloy single-layer spherical reticulated shell, a static loading test of a K6 reticulated shell with 3 rings, a 4 m span, and a 1/7 height-to-span ratio is carried out. The deformation, internal force distribution, and failure mode of the reticulated shell model are discussed. By comparing the monotone tensile test and simulation of the single member, the simulation method of rivet used in the finite element model (FEM) is obtained, and the bending stiffness and axial slip stiffness of gusset joints are calculated. Considering the joint stiffness in the FEM, the simulation results and the test fit well, indicating that the influence of the joint stiffness on the static stability of the reticulated shell cannot be ignored. In addition, by comparing the effect of different parameters of joint stiffness, the axial slip stiffness should be considered in the stability design of reticulated shells.

Framework for a finite element method-based simulation approach to fatigue assessment of welded joints using the 4R method

The increased tensile strength capacity of high-strength steels (HSS) can be utilized fully in static loads, for fluctuating loads, however, more detailed analysis of design and manufacturing is needed. This study presents a framework for investigating utilization of the finite element method (FEM) in multiparametric 4R method-based fatigue evaluation. More specifically, the aim of the current study is to produce a concept for determining the parameters of the 4R method using FEM, thus providing a tool for evaluating fatigue strength related factors numerically. The study examines gas metal arc welded (GMAW) longitudinal gusset joints made of HSS S700MC Plus. The simulation is carried out as a sequentially coupled welding analysis that includes material condition changes in the HAZ and the fluctuating response as a restart analysis. Experimental measurement is performed for comparison with the results of the numerical model in the intermediate stages of the analysis process, and in the final stage as regards fatigue life. The experimental and simulated sub-results are consistent, and the estimated fatigue lives are in relatively good agreement with the experimental fatigue results. The numerical method thus provides a tool to predict fatigue related factors considered in 4R to evaluate fatigue life of welded joints.

Experimental and numerical studies of impact loading on single-layer reticulated shells with aluminium alloy gusset joints

Aluminium alloy materials have found extensive application in large-span space grid structures. While research on the mechanical properties of aluminium alloy materials and components is generally well-established, there remains an incomplete understanding of the overall structure. Therefore, further investigation into the overall performance of aluminium alloy reticulated shells is crucial to promote their use in spatial structures, guiding structural design and addressing practical engineering challenges. This study focuses on the design of a single-layer aluminium alloy reticulated shell with a 2 m span, which was subjected to an impact test to examine its dynamic response and failure mode. By comparing and analysing stress, acceleration, and displacement time-history curves obtained from these different test conditions, the dynamic response behavior of the reticulated shell was determined. To simulate the impact on reticulated shells, explicit dynamic analysis was conducted using non-linear finite element software LS-DYNA. Based on the deformation characteristics and failure phenomena observed during the impact test, three distinct failure modes were defined for the single-layer reticulated shell. Through parameter analysis using the validated finite element model, it was determined that increasing the thickness (tp) of the aluminium alloy gusset plate or reducing the radius (R) of the gusset plate effectively enhances the overall stiffness and impact resistance of the single-layer reticulated shell. Overall, this research contributes to a deeper understanding of the performance of aluminium alloy reticulated shells under impact loads. The findings provide valuable insights for guiding structural design and addressing practical engineering problems in the field of spatial structures.

Experimental study on the hysteretic behavior of aluminum alloy gusset joint with rectangular hollow sections

Aluminum alloys were extensively applied in single-layer latticed shells owing to their exceptional mechanical properties, outstanding corrosion resistance, and aesthetic appeal. In traditional aluminum alloy grid shell structures, H-section components were widely utilized. However, the H-section components exhibited poor self-stability compared to rectangular hollow sections, whose limitation constrains the utilization of aluminum alloy single-layer latticed shells. To overcome this problem, a named ARH (Aluminum Rectangular Hollow) joint was developed using BOM bolts by some scholars, and the out-of-plane bending behavior was studied. This paper conducted out-of-plane hysteretic tests on four ARH joints with different bolt numbers and gusset thicknesses. Subsequently, a finite element model was developed to simulate the hysteretic behavior of the ARH joint. The simulation results were compared with the test results to verify the accuracy of the model. Then, a series of parameter analyses based on the developed finite element model were conducted. For the ARH joint, Analysis results showed that the decrease in bolt numbers and gusset thicknesses resulted in the weakening of the stiffness and bearing capacity, and the increase of bolt-hole diameters resulted in elevated slip deformation. Moreover, in gusset joints, joints with rectangular hollow sections have greater out-of-plane bending resistance compared to joints made from H-sections with the same section height and flange thickness.

Overload and variable amplitude load effects on the fatigue strength of welded joints

Different load spectra and individual load peaks might substantially relax high residual stresses as well as induce compressive residual stresses in welded components and, consequently, affect the fatigue performance of these joints. Consideration of peak loads and resulting relaxation of residual stresses in fatigue analyses can substantially enhance the accuracy of life prediction. The aim of the current study is to experimentally investigate the fatigue strength of welded joints subjected to different levels of overloads and variable amplitude (VA) loads and to develop local fatigue assessment method to account for the relaxation of residual stresses via a mean stress correction using the 4R method. The 4R method applies a local stress ratio for the mean stress correction considering material strength, residual stresses, applied stress ratio of external loading and local weld geometry in elastic–plastic material behaviour. Fatigue tests were carried out on fillet-welded longitudinal gusset joints made of S700 high-strength steels under applied stress ratio R = 0–0.1. A mild strength steel (S355) and ultra-high-strength steel (S1100) were selected as reference steel grades for the fatigue testing to study the material strength effects. Numerical analyses were conducted to evaluate the fatigue notch factors using the effective notch stress concept with the reference radius of rref = 1.0 mm and theory of critical distance (TCD) using the point method. The experimental results indicated that a substantial improvement in the fatigue strength capacity can be claimed in the joints subjected to tensile overloads, particularly in the studied S700 and S1100 steels. The higher-level overload (0.8fy), corresponding to the nominal cross-sectional area, improved the mean fatigue strength of the welded joints manufactured of high-strength S700 steel by approximately 60%, while the lower overload (0.6fy) improved the mean fatigue strength by 20%. In addition, a use of equivalent nominal stresses for the joints subjected to VA loads resulted in conservative assessments when employing S–N curves obtained for the CA loading. The 4R method, via the local mean stress correction for individual cycles, provided higher accuracy for the fatigue assessments.

Bearing Capacity Performance and Optimal Design of a Novel Aluminum Alloy Arch Gusset Joint.

Current research on aluminum alloy gusset joints has neglected the influences of the angle between members and the curvature of the joint plate on joint performance. This study introduces the concept of the planar angle and establishes 16 joint models using ABAQUS finite element software with parameters such as the planar angle, arch angles, joint plate thickness, web thickness, and flange thickness. The load-bearing capacity of the novel aluminum alloy arch gusset joint is theoretically analyzed, and the concepts of strong and weak axes are proposed. The failure modes and significance of different parameters regarding the bearing capacity and initial stiffness of the joint under various parameters are summarized. The results indicate that the planar and arch angles significantly affect the bearing capacity, stiffness, and failure mode of the joint.

Tensile performance of aluminum alloy roof panel-member clamp connection

In aluminum alloy reticulated shell structures with gusset joints, the roof panel is effectively connected with the structural members through a clamp connection, enabling the roof panels to participate in the force resisting system. The performance of the connection between the roof panels and the members is the foundation for studying the collaborative action of the roof panels and the members. Relevant studies have shown that when the roof panels participate in the force resisting system, there is mainly a tensile force in the roof panels perpendicular to the axis of the members. Therefore, this paper experimentally studied the mechanical performance of the clamp connection between the roof panels and the members under the tensile force in the roof panels, and employed two-dimensional plane digital image correlation (DIC) to measure the deformation of the specimen section during the entire loading process, thus exploring the force transmission mechanism of the connection. The tensile capacity of the connection can be divided into four stages: roof panel sliding, roof panel tension–shear, lower limb bending of the strip, and roof panel bending stages. The mechanical index of the connection is primarily determined by the tension–shear stage of the roof panel, and the ultimate strength and stiffness can be determined as the peak load and linear segment stiffness of the connection at this stage. The refined finite element model was further established, and it was verified that the model could efficiently simulate the mechanical properties of the connection through comparison with the test. Parametric analysis shows that with an increase in the friction coefficient between materials, roof panel thickness, angle between roof panel and flange, and bolt length adjustment, the restraint on the roof panel increases, and the failure mode of the clamp connection changes. Based on the parametric analysis, the recommended values of the friction coefficient between the materials, minimum panel thickness, minimum bolt screw depth, and maximum bolt spacing are provided. Finally, combined with the theoretical analysis, calculation formulas for the tensile strength and stiffness of the connection were proposed. A comparison with the test results indicates that the prediction accuracy of the formula proposed in this study is good.

Investigating the failure behaviour of aluminium alloy gusset joints under impact loading: An experimental and numerical study

The AAG joint, also known as the Temcor joint, is a well-established method for constructing long-span spatial grid structures using aluminium alloys. This joint system has been widely used and tested is considered a mature technology in the field. This paper investigates the tensile properties of 15 stainless-steel bolt connections for aluminium alloy plates at room temperature. Through testing, the load–displacement curve was obtained and two failure modes of the connection were identified. Test results show that the increase in the number of bolts and the thickness of aluminium alloy plate increases the ultimate bearing capacity of the connection. The thickness of the aluminium alloy plate was found to have a significant impact on the slippage effect of the bolts and the warping deformation of the contact surface. Based on the test results of the connection, three specimens of AAG joints were designed to study their dynamic behaviour under different impact loads. Our findings detail the dynamic response behaviour of joints subjected to varying impact times, including stress, acceleration, and displacement, as well as the resultant joint failure phenomenon. The test results show that AAG joints have good impact resistance. The refined FE model of the AAG joint was established using ANSYS/LS-DYNA, and its effectiveness was verified by comparing the stress, displacement, and acceleration between the numerical model and the experimental model. By comparing and analysing the final deformation of AAG joints obtained through test and numerical simulation, three distinct failure modes of AAG joints under impact load were identified. Finally, based on the stress nephogram and impact force time-history curve obtained by numerical simulation, the stiffness degradation law of AAG joints is discussed. This paper also discuss the energy dissipation mechanism of AAG joints during impact load, based on the strain energy time-history curve of each component.

Study on Flexural Performance of Aluminum Alloy Gusset Joints Subjected to Bending Moment and Shear Force

Aluminum alloy gusset (AAG) joints are widely applied in space reticulated shell structures. To investigate the flexural performance of AAG joints under the combined action of shear force and in-plane and out-of-plane bending moments, this analysis was developed by means of finite element (FE) models implemented in the non-linear code ABAQUS, and the accuracy of the FE simulation results based on the existing AAG joint test results was verified. The FE simulation results effectively described the mechanical properties of the AAG joints, including the failure mode, deformation process and bending moment-rotation curves. Furthermore, a parametric study was conducted by varying the height of the member section, the number of bolts, the radius of the joint plate, the thickness of the joint plate, the bolt preload force, and the ratio of in-plane to out-of-plane bending moments. It was found that these parameters had different effects on the bending behavior of the AAG joints.

Mechanical performance of an improved aluminium alloy gusset joint under simplex and complex load states

An improved aluminium alloy gusset joint (I-AAGJ) with two types of shear connectors (SCs) and a peripheral bending system (PBS) is proposed to address traditional aluminium alloy gusset joint (T-AAGJ) imperfections. The mechanical performance of the I-AAGJ, including axial stiffness, in-plane and out-of-plane flexural stiffness, and ultimate bearing capacity, is investigated by full-scale testing under simplex and complex load states. Numerical simulation results of I-AAGJ behaviour are presented via nonlinear finite element analysis (FEA). Three-phase models are determined to explain the I-AAGJ deformation process. In the linear phase, PBS is proven to provide significant assistance for the joint bearing axial force and bending moment. By comparing with the T-AAGJ, an at least 30% improvement of joint stiffness along three directions can be observed respectively. In the nonlinear phase, SCs strengthen the joint by delaying plastic hinge formation and preventing gusset plates from being folded. The complex load state of lower level has a negligible impact on the I-AAGJ mechanical performance, while that of higher level still has to break through the protection of PBS and SCs before it destructs the joint.

Numerical analysis of aluminum alloy reticulated shells with gusset joints under fire conditions

Numerical analysis of aluminum alloy reticulated shells with gusset joints under fire conditions

Experimental and numerical study on hysteretic behavior of Double-Layer and Single-Layer aluminum alloy gusset joints

In order to strengthen the members around holes and supports in a single-layer aluminum alloy shell, the method of laminated double-layer members is used to form a double-layer aluminum alloy gusset joint. Hysteresis behavior of this new type of joint is still unclear. Full-scale models were conducted to study the hysteresis behavior of this joint, which was subsequently compared with that of a single-layer joint. The failure mode, bearing capacity, ductility coefficient, and energy dissipation capacity were analyzed. Finite element models were built using ABAQUS to validate the test results and perform a parametric analysis. Research shows that the failure mode of the double-layer aluminum alloy gusset joint under the quasi-static test is a shear rupture of bolts, which is the same as that of single-layer joints. Compared with a single-layer joint, a double-layer joint can significantly increase the ultimate bearing capacity and ability to dissipate energy. However, the double-layer joints have poor ductility. Parametric analysis shows that the bolt material affects the ultimate bearing capacity and failure mode of the aluminum alloy gusset joints.

Stability of single-layer reticulated shells with AAG joints

Due to the advantages of light weight, high strength and corrosion resistance, aluminum alloys have been widely used in large-span space structures, and the application form is mainly single-layer reticulated shells.Considering the non-negligible stability problems of single-layer reticulated shells, this paper starts the stability research with the idea of ”member to structure”. By establishing refined numerical models of single-layer reticulated shell with aluminum alloy gusset (AAG) joints, the effective length factor of members and the overall structural stability considering the failure of the gusset joints are carried out. The main conclusions are as follows:(1) The in-plane and out-of-plane effective length factor of members of the aluminum alloy single-layer reticulated shell with gusset joints are recommended to be 1.0 and 1.9 respectively;(2) The stable bearing capacity ratio of rigid reticulated shell, semi-rigid shell, and semi-rigid reticulated shell considering joint failure is about 1:0.9:0.72. The research results of this paper provide a basis for the stable design and specification of aluminum alloy single-layer reticulated shell structures.

Experimental and numerical analysis on the bearing capacity of FGC joints under combined loading

Flower-gusset composite (FGC) joint is a new type of joint composed of cover plates, ring flower body and beams, which has good mechanical properties. In this study, the bearing capacity formula of the FGC joint under single loading was derived through the analysis of previous tests and numerical analysis. The bearing capacity and failure modes of the FGC joint under the combined action of the in-plane loading (Fh) and out-plane loading (Fv) was nalysed by bearing capacity test. The simplified calculation formula of bearing capacity of the FGC joint under combined loading was verified by bearing capacity test and numerical analysis. The results show that the bearing capacity of FGC joints is significantly better than that of traditional gusset joints. The failure mode of FGC joints are ring flower body destruction and beam failure. Based on the bearing capacity test and numerical analysis, the simplified calculation formula of bearing capacity of the FGC joint under combined loading is fitted for engineering design.

Structural performance of novel aluminium alloy gusset joints for connecting four I-section beam members

This paper presents the seismic behaviour of an aluminium alloy grid shell structure with due consideration of the rotation performance of its two novel gusset joints. The two novel aluminium alloy gusset joints were designed for connecting cross-arranged I-section beam members by stainless steel swage-locking pins and stainless steel bolts. One full-scale gusset joint was tested under monotonic loading, with the failure mode, load-displacement response and stiffness classification fully reported. The solid-based refined finite element (FE) model of the joint was developed by using Abaqus program and validated against test results. Based on the validated FE model, parametric studies were performed to investigate the effect of key parameters, including the shape of gusset plates, the preload of fasteners, angle shear connector configurations, and the number and layout of pins, on the structural performance of the novel gusset joints. The failure modes, moment-rotation curves, initial stiffness and ultimate design resistance were identified and compared in groups for joint design optimization. The cyclic behaviour of two optimal gusset joints was numerically analysed, and then incorporated in the fibre-based macro FE model of the aluminium alloy grid shell structure developed by using OpenSees program. The seismic performance of the grid shell structure subjected to different earthquake hazard levels, including the displacement, joint rotation, beam stress and shear base responses, was comprehensively evaluated. Sound earthquake resistance of the aluminium alloy grid shell structure is demonstrated, with safety and reliability of the novel gusset joints used in it.